Potentiometer



Jan. 17, 1950 H, GULLER 4 2,494,998

' POTENTIOMETER Filed. Feb. 10, 1948 2 sheets-sheet 1 yaw Inventor Harold Gu/ler 4:21pm 15? M3 5 Jan. 17, 1950 H. GULLER 2,494,998

POTENTIOMETER Filed Feb. 10,. 1948 v 2 Sheets-Sheet Inventor Harold Gu/ler WW E M55 v Patented Jan. 17, 1950 POTENTIOMETER Harold Guller, Richmond Heights, Mo., assignor to Essex Manufacturing Company, St. Louis, Mo., a corporation of Missouri Application February 10, 1948, Serial No. 7,380

5 Claims.

This invention relates to rheostats or variable resistances and more particularly to potentiometers adapted to control currents of medium voltage and it has for its main object to provide a potentiometer assembly contained within the handle gripped by the operator which operates without gear, producing a Wide variation of the resistance over a, relatively small angle which the operator can directly cover by a movement of his hand.

It is a further object of the invention to provide a potentiometer construction contained within a handle gripped by the operator which indicates automatically to the operator the approach of the end of the angular movement by an increased resistance against movement.

It is a still further object of the invention to provide a potentiometer of the above mentioned type which is not only positively arrested in its end positions but which produces an increased resistance against further movement near said end positions, while at the same time keeping the electrical resistance at a constant value.

It is a further object of the invention to provide a, potentiometer contained Within a handle which uses twin or double wipers operating simultaneously on two resistance elements.

It is a further object of the invention to provide a potentiometer using a pair of twin or double wipers adjusted simultaneously.

Further and more specific objects can only be explained in connection with the detailed specification or will be apparent from such specification.

The invention is illustrated in the accompanying drawing showin one modification by way of example. Other embodiments, some of which will be obvious to the expert skilled in this art, have not been illustrated and described, as the inventive concept and the principle of the invention may be explained by referring to a preferred mode of applying said principle. Modifications of the example shown, therefore, do not necessarily entail a departure from the invention.

In the drawings:

Figure 1 is a perspective outside view of the potentiometer.

Figure 2 is a, sectional elevational view of the potentiometer the section being taken along line 2-2 of Figure 4.

Figure 3 is a sectional elevational view, the section being taken along line 3-3 of Figure 4.

Figure 4 is an elevational sectional view, the section being taken along line 4-4 of Figure 2.

Figure 5 is a view of the normall cylindrical potentiometer coil when flattened so as to lie in a plane.

Figure 6 is an exploded perspective view of the two inner members which are arranged one within the other.

Figure '7 is a sectional elevational view, the section being taken along line l--l of Figure 4.

Figure 8 is a view of a detail.

Figure 9 is a view of the lock ring used in connection with the groove in the spindle.

Figure 10 is a wiring diagram.

Figure 11 is a perspective view of a detail.

The invention is shown and described by way of example in connection with a potentiometer, such as used for'the fine adjustment of control instruments or the like, operating with currents within a medium voltage range between, say 10-100 volt; The complete potentiometer structure is contained within the cylindrical casing, generally indicated at H, which also forms the handle or grip and which therefore is of such a size that the hand of the operator may grip and encircle it. Likewise, the length of the container is smaller than the hand of the operator. It is essential in such a completely closed structure that the heat developed by the potentiometer should-not be noticeable or cause any discomfort and that the operator who is observing the instrument or the apparatus with which the potentiometer is connected, but is not observing the latter, should be informed when he is close to or has reached the limit to which the instrument may be moved in order that he may not attempt toproduce further movement by using force.

Accordingly the potentiometer assembly as shown comprises a central core or base member l2 shown partly in section in Figure 4 and in perspective view in Figure 6, which is provided with a, foot flange I3 adapted to be fixed to a supporting member by means of threaded bolts !4 projecting therefrom. This core or base mem-- her is hollow and is provided at its end with a tubular sleeve like head portion it of reduced diameter with a central bore ll which forms a bearing journalling the potentiometer spindle 30. The base or core member i2 is provided with two small bores I8, l9 each holdin a pin or wire 20, 2|, respectively,-projecting into the hollow interior of the base member. One of these wires (20) is soarranged that it lies directly on the inner wall of the hollow base while the other wire (2|) projects freel into the interior for a purpose described below.

The spindle member is generally indicated at 30 and is located within the hollow interior of the core or base member and within the bore l1. It comprises the cylindrical spindle proper 24, carrying at one end a threaded bolt and at the other the detent drum 25. The member 24 has flattened portions 21 near the end carrying the bolt 26 which permit a coupling of the said member with the outer member or cover 60 for rotation.

The spindle 24 is also provided with an annular locking groove 28 into which a locking ring 32 (Figure 9) may be inserted. When the spindle member 30 is correctly mounted within the base member, the detent drum 25 abuts against the inner wall of the base member while the annular groove is located outside the sleeve Hi.

When the lock ring 32 is inserted into the groove 28, the spindle member 30 is positively locked in an axial direction, while at the same time journalled within member I 6 and free to rotate within the same.

The detent drum 25 is in general of a cylindrical shape, fitting into the hollow interior of the base member, but is provided with a deep recess 33. This recess may be provided with two arcuate or near semi-circular portions 34, 35 arranged at an angular distance from each other with respect to the axis of the drum which is approximately equal to the angle through which the potentiometer may be turned in order to obtain the maximum change in resistance.

The drum, moreover, is provided with a transverse cylindrical bore 36, one end of which (31) has a somewhat reduced diameter while the other end (38) is slightly wider and is screw threaded.

A ball 42 is held within the bore 31 against which a piston like member 44, slidably mounted in the bore 35 presses. This member is itself pressed towards the ball by a spring 45 which is inserted into the bore 36 and which finds its support in a plug 39 screwed into the threaded end 38.

When the spindle member carrying the detent drum 25 and the above described members held therein has been inserted into the interior of the base member l2 the ball member 42 held in the bore 31 which is somewhat smaller than the largest diameter of the ball, does not ride on the wall of the base member. There is therefore no considerable resistance against rotational displacement. However when the ball meets pin or wire 20 which is held in contact with the wall of the base member, the resistance increases markedly as, in order to obtain a further rotational movement, the ball and the piston has to be pressed back against the action of spring 45.

The second pin or wire 2| is so arranged that it can cooperate with the walls of the recesses 34 and 35 and it acts as a stop for the movement of the spindle. Figure 7 shows the extreme position in which a counter-clockwise movement of the spindle member has been stopped by wire 2| abutting against recess wall 35. This is a position which can only be reached after overcoming a marked increase in resistance due to the ball being moved over wire 20. Likewise, if now the spindle (looking towards the front end of the potentiometer) is turned clockwise in the direc tion of the arrow, which is the sole direction in which the spindle can be turned, an increased resistance has first to be overcome which however after having turned the spindle through an angle of several degrees (between 4 and 20 in actual practice) decreases suddenly when the ball 42 has cleared the wire 20 and from this point on only a relatively small resistance against rotation will be felt, until when turning the spindle, the wire 2| enters the second semi-circular stop recess 34 and arrests further motion.

The core or base member serves as a support for the coil 50, which consists of the coil form 52 011 which the resistance wire is wound. In the example illustrated four groups of wire windings forming the variable resistance elements 46, 41, 48, 49, are used. They may all have the same resistance value. Each resistance element is a separate element the ends of which are either unconnected or are connected with copper strips 5 I, 53, 54, 55 provided with eyelets or other means for fastening the resistance wires to them, which may or may not also carry means for attaching lead in wires.

The four resistance elements are used in pairs with the wipers sliding over the small front sides located in a plane at right angle to the axis of the cylindrical base I2. One wiper element, as explained below, cooperates with a pair of resistance elements. At the end each resistance element is provided with a number of windings 59 which pass through slots 58 located immediately behind the end on which the wipers are sliding. When the wiper slides over these ends, the resistance will therefore not change noticeably.

The coil form 52 may be split and it then consists of one or two strips held on the base by screws (not shown) passing through the form.

The outer cover 60 of the potentiometer serves simultaneously as a handle, and is of such size that it may be gripped and held by the hand of the operator which may practically cover it.

This handle and cover member 60 may have the form of a cup and may be made of a single piece. In the example shown the cylindrical surface is knurled or milled (at 52) and the flat bottom surface 62 has been provided with recesses in the form of a cross into which a cross piece 53 of a special alloy material has been inserted. A recess 64 in this member takes up the nut 65 screwed on bolt member 28 and holds the cup shaped handle member on the spindle member 30. As will be seen the cylindrical portion of the cup shaped member 60 also slides on the foot member I3 so that the potentiometer is completely enclosed by the cover.

The central part of the bottom portion 63 is provided with an opening with flattened sides which fit the flattened portions 21 of the spindle member 24, so that a rotational movement of the cup shaped cover 60 will be transmitted to the spindle 30.

Behind the bottom portion 62 a wafer disk 65 of Bakelite or of a similar plastic material is mounted and is held in any appropriate manner against the bottom, for instance by means of an adhesive and by a thrust washer 61. This water disk carries the wipers 68, 59, which are double wipers with a central portion I0 fixed on the wafer disk 66 by eyelets H or other clamping means. Each wiper 68, 69 comprises two elastic Wiping tongues 12, 13 which are applied against the front ends (seen in Figure 2) of the coil resistance elements.

The lead in wires 15 of the coil pass through the interior of the hollow base member and through holes 16 in the cylindrical part into which insulating spacers 11 are pressed. They are connected either with the copper strips 5|, 55 holding the eyelets for the resistance or with a special copper strip 18.

As mentioned previously the wipers are double wipers sliding on two resistance elements simultaneously. Figure shows the connections of the four elements in such a case. The customary three potentiometer connections are marked A, B, C in Figures 5 and 10. The connections of the potentiometer explain themselves.

In operation the operator turns the cover handle 60 in the desired direction to increase or decrease the resistance. The torque necessary to move the handle is small as long as the detent balls travels above the smooth cylindrical interior surface of the base member. When the wiper has arrived approximately at the end of the resistance, the ball of the detent cylinder has also been turned so as to be in contact with Wire 20. Further rotation requires a much larger torque and therefore manifests itself in a greater exertion necessary to turn the handle. During this movement the resistance may either still increase or may remain constant with the wipers moving over the ends 59 of the wire passing through slots 58. When the ball has passed over the wire the handle is arrested by wire 2| falling into recess 35.

When attempting to move the handle back, the handle still offers a large resistance, indicating that no change of resistance takes place as long as the ball moves over wire 20. From this position to the position at the other end resistance again is light. At the other end, the handle is arrested when the recess 34 in the detent cylinder strikes the wire 2 I.

It will be clear that minor constructive changes and especially constructive changes of an unessential nature do not aiiect the inventive concept.

Having described the invention, what is claimed as new is:

1. A rheostat comprising a hollow substantially cylindrical base member, resistance units mounted on the outside of said base member provided with windings partly extending along said cylindrical member and partly at right angle thereto, a spindle member rotatably held in the hollow interior of said base member, a cylindrical outer handle member enclosing the base member and the resistance elements completely, said cylindrical outer handle member being fixedly connected with said spindle member, wipers carried on the inside of said outer cylindrical member, cooperatin with the windings which are at right angle to the cylindrical base member, a cylindrical detent member fixedly associated with said spindle memher and provided with a stopping recess the walls of said recess being spaced for limiting the rotational movement of the base member around the axis of the spindle member, a projecting stopping pin moving within said recess and held in the base member, a spring pressed member carried by said cylindrical detent member, pressed against the inner cylindrical surface of the hollow interior of the base member, and a pin extending along and partly projecting from the inner cylindrical surface arranged in the path of said spring pressed member, for increasing the mechanical resistance against further rotational movement.

2. A rheostat comprising a hollow substantially cylindrical base member, resistance units mounted on the outside of said base member, provided with windings partly extending along said cylindrical member and partly at right angle thereto, a spindle member rotatably held in the hollow interior of said base member, a cylindrical outer handle member enclosing the base member and the resistance elements completely, said cylindrical outer handle member being fixedly connected with said spindle member, wipers carried on the inside of said outer cylindrical members, sliding on the windings which are at right angle tothe cylindrical base member, a detent cylinder arranged within the hollow cylindrical base member, fixedly associated with said spindle and provided with a recess, the walls of the recess being spaced for limiting the movement of said spindle member around the axis of the base member, an arresting pin projecting axially from said base member and entering said recess, thus arresting the spindle member in its end positions, a trans- Verse bore within said detent cylinder, a spring pressed piston therein, a ball pressed by said piston and moving on the inner cylindrical wall of the hollow base member, a further axially extending fixed pin applied against and partly projecting from the inner Wall of the cylindrical base member, said pin being arranged in the path of said ball and so located as to come into contact with said ball upon rotation of the outer memher and spindle member, when the arresting ,pin is a short way from arresting the detent member in its end position.

3. A potentiometer comprising a hollow substantially cylindrical base, a spindle member carried by and rotatably held within the hollow in terior of said cylindrical base member, an outer substantially cylindrical handle memberfcompletely enclosing said cylindrical base member and fixedly connected with said spindle member, a potentiometer coil including a coil base and a plurality of windings forming separate resistance elements carried on the outside of said base member, and enclosed by said outer handle member, said windings having longitudinal portions running along said cylindrical base members and transverse portions at right angle thereto, and being provided with end portions substantially without longitudinal extension showing substantially the same resistance on their transverse portions, a set of double wipers, each double wiper being in contact with two resistance elements, carried in the interior of said outer cylindrical member and movable with the same, said wipers slidin on the portions of the windings at right angle to the cylindrical base members, and a detent member carried by said spindle member provided with means for increasing the mechanical resistance against rotation when the wipers slide over said end portions of the resistance elements.

4. A potentiometer comprising a hollow substantially cylindrical base, a spindle member carried by and rotatably held within the hollow interior of said cylindrical base member, an outer substantially cylindrical handle member, completely enclosing said cylindrical base member and fixedly connected with said spindle member, a potentiometer coil including a coil base and a plurality of windings forming separate resistance elements carried on the outside of said base member, and enclosed by said outer handle member, said windings having longitudinal portions running along said cylindrical base members and transverse portions at right angle thereto, said win-dings being provided with end portions substantially without longitudinal extension showing substantially the same resistance on their transverse portions, a set of double wipers, each double wiper being in contact with two resistance elements, carried in the interior of said outer cylindrical member and movable with the same, said wipers sliding on the portions of the windings at right angle to the cylindrical base members, a cylindrical detent member provided with a recess and fixedly connected with said spindle member, an arresting pin projecting from said base member entering said recess for arresting said detent cylinder and spring pressed means held within said detent cylinder for increasing the mechanical resistance against rotation near the position in which said spindle member is arrested.

5. A potentiometer comprising a hollow' substantially cylindrical base, a spindle member carried by and rotatably held within the hollow interior of said cylindrical base member, an outer substantially cylindrical handle member, completely enclosing said cylindrical base member and fixedly connected with said spindle member, a potentiometer coil including a coil base and a plurality of windings formin separate resistance elements carried on the outside of said base member, enclosed by said outer handle member, said windings having longitudinal portions running along said cylindrical base members and transverse portions at right angle thereto, said windings being provided with end portions substantially without longitudinal extension showing substantially the same resistance on their transverse portions, a set of double wipers, each double wiper being in contact with two resistance elements, carried in the interior of said outer cylindrical memher and movable with the same, said wipers sliding on the portions of the windings at right angle to the cylindrical base members, a cylindrical idetent member arranged within the hollow cylindrical base member, fixedly associated with said spindle and provided with a recess, an arresting pin projecting axially from said base member and entering said recess, for arresting the spindle member in its end positions, a transverse bore Within said detent cylinder, a spring pressed piston therein, a ball pressed b said piston and moving on the inner cylindrical wall of the hollow base member, a further axially extending fixed pin applied against the inner wall of the cylindrical base member, said pin being arranged in the path of said ball and so located as to come into contact with said ball upon rotation of the outer member and spindle member, when the arresting pin is a short way from arresting the vdetent member in its end position, and when the Wipers are moving on the end portions of the resistance elements.

HAROLD GULLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA PE NTS Number Name Date 1,516,526 Ganss Nov. 25, 1924 2,144,137 Batcheller Jan. 17, 1939 2,177,285 Schellenger Oct. 24, 1939 2,206,882 Davis July 9, 1940 2,411,891 Owens Dec. 3, 1946 

